Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08H—DERIVATIVES OF NATURAL MACROMOLECULAR COMPOUNDS
  • C08H6/00—Macromolecular compounds derived from lignin, e.g. tannins, humic acids
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G8/00—Condensation polymers of aldehydes or ketones with phenols only
  • C08G8/28—Chemically modified polycondensates

Definitions

• Lignin like phenol, easily form condensation products with carbonyl compounds such as formaldehyde. Unlike the phenols, the lignin, on account of its high degree of polymerization, contains fewer phenolic hydroxyl-groups and thereby fewer active sites on the aromatic ring for linking with e.g. formaldehyde. If unmodified lignosulfonate is condensed with formaldehyde a three-dimensional network (a resin) will certainly be obtained but it will have a limited number of linking points and therefore will be more brittle and weaker than a phenol formaldehyde resin. Furthermore, sulfonic acid groups will enhance the water swellability of the network, which means an impairment of the water resistance of the bonded product.
• the object of our invention is to provide an improved process over what has gone before.
• the first step is an acid condensation step wherein a smaller amount of formaldehyde is caused to react with phenol and sulfite waste liquor at a temperature of at least 80°C and at addition of acid to a pH within the range of 0.2 to 4.0.
• This first step acid condensation is preferably carried out to the extent that at least 40 percent of the phenol is present in bound form.
• the reaction products are cooled.
• the first step acid condensation can be carried out under pressure in an autoclave, or at atmospheric pressure.
• the water content of the reaction mixture in the first step is suitably 20 - 100 percent by weight of the combined weight of sulfite waste liquor and phenol.
• the sulfite waste liquor can for example be unmodified sulfite waste liquor, such as spent liquor or spray-dried powder and suitably contains at least 70 percent by weight of lignosulfonate and at most 12 percent by weight of sugar, based on the dry substance.
• unmodified sulfite waste liquor such as spent liquor or spray-dried powder
• the acid pre-condensation is assumed to proceed according to two different courses; on the one hand a condensation between lignin and phenol to a ligno-phenol condensation product, (which is previously known in the literature), and on the other hand a condensation between built-up ligno-phenol units and formaldehyde wherein the formaldehyde is assumed to have a quite conventional function and act as a methylene donor for the building-up of high-molecular condensation products of the novolac type.
• the second step is an alkaline condensation step wherein the cooled reaction products of the first acid condensation step are further condensed under alkaline conditions at a temperature of at least 60° by adding more formaldehyde and enough alkali so that the pH exceeds 7.
• the water content during the second step is 40 - 60 percent by weight based on sulfite waste liquor and phenol.
• the pH in the alkaline condensation step is preferably between about 10 - 13.
• the pH in the alkaine condensation step may be lower, i.e., within the range of about 7 - 10.
• 10 - 60 parts by weight of sulfite waste liquor (dry content) is pre-condensed in acid medium, with 90 - 40 parts by weight of phenol, 2.5 - 30 parts by weight of formaldehyde and 20 - 100 parts by weight of water at a pH within the range of about 0.2 - 4.0, the condensation is then continued in an alkaline medium at a pH of 10 - 13 after addition of more formaldehyde and water to a total amount of formaldehyde of 30 - 75 parts by weight.
• Seven resins were prepared with varying compositions and under varying condensation conditions.
• the variables involved in the seven examples are indicated with X 1 , X 2 . . . , X n , which are listed in table 1 and explained below.
• compositions and pH of the reaction mixture are shown below:
• a first step acid condensation was carried out in such a way that the mixture was heated to reflux.
• the temperature at that point was 97°C and the time for heating from room temperature to 97°C was 30 - 45 minutes.
• the time at 97°C was X 8 min.
• the amount of bound phenol was determined to be X 9 percent.
• the reaction mixture was cooled to 20°C and then X 10 parts of water and X 11 parts of formaldehyde in the form of formalin were added. Furthermore sodium hydroxide in the form of a 40 percent aqueous solution was added making the pH rise to X 13 .
• the total water content of the mixture was X 14 parts.
• the alkaline condensation step was carried out in such a way that the mixture was heated to 80°C.
• the heating time was about 30 min.
• the pH and the viscosity were checked at regular intervals, the pH being adjusted by successive additions of sodium hydroxide in order to keep the pH within the range of 10.5 - 11 at the beginning of the condensation and 11 - 12 at the end of the condensation.
• the total amount of the added sodium hydroxide was X 12 parts.
• the condensation was interrupted by cooling of the resin to room-temperature.
• the pH of the resin was X 15 and its viscosity X 16 cP (measured with a Brookfield-viscosimeter at 50 r.p.m. and at 25°C after adjustment of the water content to 60 percent.)
• the so-called gelling-time was X 17 min. at 100°C with a Tecam gelling-time meter.
• Example 6 was not conducted according to our invention as there was no formaldehyde present in the acid condensation step.
• the amount of acid is high (X 4 ) and a time of condensation of 480 min. (X 8 ) is required to get an amount of bonded phenol of 17.5 percent.
• X 4 the amount of acid is high
• X 8 a time of condensation of 480 min.
• particleboards were made with the resins as binders in a half-scale apparatus.
• particle raw material so-called core particles were used, which had been dried to a suitable moisture content of approximately 4 percent.
• the particles were coated with a resin solution of a suitable dry content (40 - 50 percent) and of a suitable viscosity (90 - 180 cP) in a rotating drum.
• the amount of resin was 10 percent on dry basis, based on dry particles.
• the resins were used as such, i.e., without any addition of a supplementary curing agent or hydrophobing agent.
• the particles were formed into sheets and were pressed between press plates at a pressure of about 18 kp/cm 2 and at a press temperature 165°- 170°C.
• the pressing time was 10 min.
• the pressed particleboards were post-conditioned.
• the particleboards were tested according to standard methods. All the boards had in the dry state values for flexural strength and internal bond which exceeded valid DIN-standard specifications for particleboard bonded with phenolic resins. These standard values are 180 kp/cm 2 for the flexural strength and 3.5 kp/cm 2 for the internal bond.
• the reaction mixture was heated to boiling. The time for heating from room temperature up to reflux temperature was bout 45 min. The condensation was then continued to a viscosity of about 900 cP (Haake viscosimeter, testing device cone-plate), shear rate 5650 S.sup. -1 25°C). The total condensation time at reflux was about 2 hours, the ligno-phenol then being cooled to about 40°C. The amount of bound phenol was at that time approximately 60 percent.
• a glue solution was prepared from resin (dry content 43 percent), a wax emulsion (dry content 50 percent) as hydrophobing agent and a curing-agent (potassium carbonate as a 50 percent aqueous solution).
• a glue solution of 40 - 42 percent was prepared according to the following recipe:Composition of the Surface layer Middle layerglue (parts) (parts)_____________________________________________Lignin resin accordingto this example 200 200Spg-wax-emulsion 7.5 7.5Potassium carbonate 0 12Water 5 0______________________________________
• Particles were coated with the glue solution, prepared as above, in continuous glue machines by means of a series of spray nozzles, where the particles were kept in rotation by an agitator in order to spready the adhesive as evenly as possible over the surface of the particles.
• the particles were sheeted by means of four separate particle spreading units in such a way that the surface particles were spread by the first and the last unit and the core particles spread by the intermediate units.
• the pressing was accomplished in a hydraulic press with eight platens and with steam-heated press plates. The pressing was carried out intermittently and without pre-pressing.
• the press temperature was 160°C and the pressing time was varied between 9 - 15 min.
• Particleboards were produced with a trimmed size of 360 ⁇ 120 cm and with a thickness of 20.5 mm before grinding.
• the volume weight varied between 740 - 760 kg/m 3 .
• the boards were tested unground both immediately after pressing and after a storage of 15 - 20 days.
• a resin was prepared according to the following and evaluated for laminating use.
• the reaction was interrupted when a viscosity of 80 cP (according to Hoeppler) measured at 20°C, was reached. 700 ml water was distilled off under vacuum and at a temperature of about 50°C.
• a viscosity of 80 cP according to Hoeppler
• 700 ml water was distilled off under vacuum and at a temperature of about 50°C.
• After sheets of phenolic film and one decorative sheet of melamine film were pressed together and the laminate was then tested for water absorption and dimensional change according to NEMA standards LD 1-2.7 and LD 1-2.8. The following results were obtained: Water absorption 10.0 percent, dimensional change 0.22 percent and 0.90 percent respectively.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Biochemistry (AREA)
• Materials Engineering (AREA)
• Phenolic Resins Or Amino Resins (AREA)
• Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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Cited By (14)

Citations (3)

• 1973
  • 1973-02-21 SE SE7302412A patent/SE371645B/xx unknown
• 1974
  • 1974-02-20 NO NO740573A patent/NO740573L/no unknown
  • 1974-02-21 FI FI509/74A patent/FI57431C/fi active
  • 1974-02-21 US US05/444,447 patent/US3940352A/en not_active Expired - Lifetime

Patent Citations (3)

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